The present invention relates to a spring clutch mechanism for transferring the rotation in an electrophotographic copying machine.
An electrophotographic copying machine employs a clutch mechanism for driving an original carrier or an exposure system. A typical construction for driving an original carrier in an electrophotographic copying machine is disclosed in U.S. Pat. No. 4,108,544, DRIVING MECHANISM FOR TRAVELLING ORIGINAL CARRIER IN AN ELECTROPHOTOGRAPHIC COPYING MACHINE, issued on Aug. 22, 1978. The conventional spring clutch mechanism requires a considerably large force to activate the clutch mechanism. Thus, the system becomes complicated, and the response is considerably slow in the conventional system.
Accordingly, an object of the present invention is to provide a spring clutch mechanism of a simple construction.
Another object of the present invention is to provide a spring clutch mechanism which requires a slight force to activate the clutch mechanism.
Still another object of the present invention is to provide a spring clutch mechanism which shows a rapid response.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a coil spring is disposed around coaxially disposed bosses of a driving shaft and a driven shaft. One end of the coil spring is fixed to the boss of the driving shaft. A first sleeve is disposed around the coil spring. A second sleeve is slidably secured to the first sleeve so that the second sleeve is slidable on the first sleeve in the axial direction and rotates in unison with the first sleeve. A clutch activating force is applied to the second sleeve in the axial direction in order to push the second sleeve toward a flange portion of the boss of the driven shaft.
In the non-transmitting mode, the boss of the driving shaft is driven to rotate by the drive source. The coil spring, the first sleeve and the second sleeve rotate in unison with the rotation of the boss of the driving shaft. However, the driven shaft does not rotate. To transfer the rotation of the driving shaft to the driven shaft, the clutch activating force is applied to the second sleeve in the axial direction for pressing the second sleeve against the flange portion of the boss of the driven shaft. Since the boss of the driven shaft is held stationary, the braking force is applied to the second sleeve. Therefore, the rotation of the first sleeve is braked, whereby the coil spring is tightly bound around the bosses of the driving shaft and the driven shaft. In this way, the rotation of the driving shaft is transferred to the driven shaft. The rotation of the driven shaft is stopped when the clutch activating force is removed.